code: def _xml(self, prefix=""):
      s = ""
      if self._x:
          s += 'x="%s" ' % repr(self._x)
      if self._y:
          s += 'y="%s" ' % repr(self._y)
      if self._width:
          s += 'width="%s" ' % repr(self._width)
      if self._height:
          s += 'height="%s" ' % repr(self._height)
      return s
  
file_path: vispy/vispy/util/svg/viewport.py
imports: from .length import XLength, YLength
label_desc: Use image node_id 8 for calling the Viewport obj's underlying member method code with example usage: obj._xml(prefix) and returns: s